A network is most useful if connections, such as links between clients and network servers, are reliable and network devices, for example servers, can quickly receive and respond to numerous incoming requests from clients or other devices on the network. As processing speeds increase and memory access time decreases in servers and other network devices, throughput at device interfaces to the network can become a bottleneck. Network reliability and throughput can be improved by coupling some or all of the network devices to the network through redundant network resources. Redundant network links may be formed using multiple single-port Network Interface Controllers (NICs), one or more NICs each having more than one port, or a combination of single and multiple port NICs. Network interface resources can be teamed to improve throughput and reliability. Resource teams typically include two or more NICs, or two or more NIC ports, which are logically coupled in parallel to appear as a single virtual network adapter to the other network devices. Resource teams can supply aggregated throughput of data to and from a network device employing the team and/or fault tolerance with resource redundancy enabling an increase in reliability.
Fault tolerant teams of network resources can employ two or more network adapter or NIC ports with one port “active” and configured to operate as a “primary,” and other members of the team designated as “secondary” and configured to operate in a “standby” mode. A NIC or NIC port in standby mode is usually idle. Typically activity may be limited to an extent sufficient to respond to system test inquiries or heartbeats which indicate to the team that the NIC or port remains operational. The NIC or port in standby may be activated to replace the primary adapter upon failure. Thus, interruption of a network connection to a critical server may be avoided notwithstanding the existence of a failed network adapter card or port.
Failover is a capability to switch automatically to a secondary resource, typically a redundant or standby network resource, upon failure or abnormal termination of a previously active primary resource.